I'm trying to get Tunnel Mouse, and repaired the projector in Rainbow Falls; is there some way to unlock the DEC there to Devil Falls? The room is no longer allowing me to interact with any of the controls. Can I go through the DEC from the other side?

Update: answering my own question, in case anyone else runs into this problem. The DEC can be unlocked by going through from the Devil Falls entrance. This counts for the achievement progress.